1. Field of the Invention
The present invention relates to a method of producing a semiconductor pressure sensor, and more particularly, to a method of producing a diaphragm type semiconductor pressure sensor.
2. Description of the Related Art
Regarding a conventional process of producing a diaphragm type semiconductor pressure sensor, a surface pattern including a gauge resistance, a wiring ,and an aluminum pad and the like is formed on the front surface of a semiconductor substrate whose front surface is mirror surface in a front-end process. Next, in the back-end process, the thickness of the semiconductor substrate is reduced by polishing the rear surface of the semiconductor substrate, and a concave portion is formed by wet etching of the semiconductor substrate using an etching mask (silicon nitride film) which is formed on the rear surface of the semiconductor substrate by plasma CVD method, so that the bottom surface of the concave portion functions as a diaphragm (JP, 09-45928, A).
However, when the rear surface of the semiconductor substrate is polished in the back-end process, there arises a problem that damages or scratches are formed on the rear surface, so that the diaphragm surface (the bottom surface of the concave portion) becomes rough. As the adhesion of the etching mask for forming the concave portion is not good, there arises another problem that the control of the shape of the diaphragm (concave portion) with high dimensional accuracy is difficult.